Optical confocal microscopy has become a popular technique to produce images in biological tissue with lateral resolutions of 0.5 to 1 μm and comparable axial resolutions. The technique collects reflectance or fluorescence images ex vivo and is rapidly growing as an in vivo diagnostic tool. Applications include imaging basal cell carcinomas, assisted Moh's surgery, and studies of the oral mucosa. A disadvantage of this technique is the lack of penetration at depths higher than 300 to 350 μm in human skin, because of multiple scattering contributing to the optical noise as well as discontinuities in the optical properties at the dermo-epidermal junction and below.